Process for the partial liquefaction of gas mixture by means of pressure and intense cooling



J1me ".1958 8 R. BECKER ET AL PRDQESS FORv THE- PARTIAL LIQUEFACTION OF GAS MIXTURE BY MEANS OF PRESSURE AND "INTENSE COOLING Filed July 27, 1954 nited States Patent PROCESS FOR THE PARTIAL LIQUEFACTION 0F GAS MIXTURE BY MEANS OF PRESSURE AND INTENSE COOLING Rudolf Becker, Munich-Solln, and Wilhelm Hartmann, Munich, Germany, assignors to Gesellschaft fiir Lindes Eismaschinen Aktiengesellschaft, Hollriegelskreuth, near Munich, Germany Application July '27, 1954, SerialNo. 446,098 Claims priority, application Germany August 12, 1953 4 Claims. (Cl. 62-17,5.5)

The present invention relates to a process and an apparatus, for thepartial liquefaction of gas mixtures by means of pressure and intense cooling with concentration a circuit is usually employed in which a part of the highpressure gas is expanded to mediumpressure and returned into the circuit with utilisation of the cold thus produced, which is transferred to high-pressure gas to be It is an object of the. present invention to provide a process for the partial liquefaction of gas mixtures by means of pressure and intense cooling, with concentration of the less readily-boiling components of said mixtures, and in which the work-performing expansion of compressed gases is utilized to generate cold, comprising the steps of compressing a gas mixture to a relatively low pressure of a few atmospheres, cooling the compressed mixture in a first, reversible heat-exchange zone, re-heating a minor part of the cooled, compressed mixture in heat-exchange with said mixture to approximately the temperature of the latter, partially liquefying said minor part by cooling the same in heat-exchange with the remainder of the cold, compressed gas mixture, in a second heat-exchange zone and by throttling, expanding said remainder in a work-performing manner after said second heat-exchange zone, combining the resulting expanded gases with the non-liquefied portion of said minor part, and leading the resulting cold, expanded mixture through said first reversible heat-exchange zone to provide a source of cold for the latter.

The invention has for one of its objects the liquefaction of gases with a minimum expenditure of power and using gases of substantially lower pressure, that is to say, either gases brought to a uniform medium pressure of 6 to 40 atmospheres gauge or substantially low-pressure gas and a relatively small quantity of high pressure gas.

A main gas quantity compressed to a low-pressure of about atmospheres gauge is pre-cooled with non-liquefied residual gas or a part of the gas freed from carbon dioxide and other impurities by condensation, and guided in tubes within the regenerators, and the main part of this gas, after intermediate heating in exchange with gas to be liquefied, is expanded so as to perform work and led out of the liquefier through one of the regenerators, together with residual gases. The fraction of this gas which is re-heated in the regenerators is thereafter compressed, cooled, then expanded so as to perform work, and cooled in exchange with gas at a low temperature and pressure directly before the work-performing expansion of the latter and, at the same time, liquefied and expanded. After separation of the liquid from the fraction which has remained gaseous, the residual gas is discharged in heat exchange with crude gas, together with the partial quantity subjected to work-performing expansion.

For a better understanding of the invention and to show how the same is to be carried into effect, reference will now be made to the accompanying drawings, in which:

Figure 1 is a flow sheet indicating one constructional form of an apparatus for the partial liquefaction of gas mixtures,

Figure 2 illustrates a modification of the constructional form of Figure 1. I 7

Referring now particularly to Figures 1 and 2, this indicates the following possible line of flow:

The air is first compressed to about 5 atmospheres in a low-pressure compressor 18 and the air fraction to be liquefied, which is freed from impurities in a regenerator 2 and re-heated in tube exchangers 8 and 9, is then compressed to about 200 atmospheres in a high-pressure compressor 7, and, after pre-cooling in a cooler 10, for example the evaporator of a refrigerating machine (not shown), expanded while performing .work in an expansion engine 6 to a pressure which is sufficient for liquefaction in exchange with colder gas in a liquefier 4. This air-fraction is separated into a liquid phase having a high oxygen content and a gas phase as described above. The liquid is fed to. its place of use and the gas phase is combined with the main air fraction which has been expanded in a turbine 5, and re-heated together with the said fraction in a second regenerator. The air purified by condensation of the impurities in the regenerators 2 and 3 subjected to a cold blast is cooled to such an extent in the said regenerators, 2., 3, that it is capable of liquefying a substantial proportion of the air expanded to liquefaction pressure in the expansion engine 6, in indirect heat exchange in the liquefier 4. The cold produced in the work-performing expansion ,of the highpressure air which is pre-cooled by separate cold thus effects the further cooling of the expanded air, the lique faction of which, however, is efiected by the cold gas coming from the regenerators 2, 3. The cold required for this purpose is provided substantially by the expansion of the main part of the air in the expansion turbine 5. The cold supplied by this turbine 5 is, for this purpose, previously transmitted to the regenerator 3 to be blown cold, and is stored therein. When the regenerators 2, 3 have been changed over, the stored cold is transferred to fresh gas, which is thus cooled almost to the condensation point and liquefies by indirect cold transfer the more highly compressed portion of the air in liquefier 4.

Instead of a single-stage turbine 5, a two-stage turbine 5a, Sbmay be employed in the apparatus of Figure 1 .(see Figure 2). The gas expanded in the first stage 511 is fed to the second stage 5b only after intermediate heating in the exchanger or liquefier 4, and the gas expanded in the latter stage is discharged through the regenerator 3. The cold output of this arrangement is, as known,

' higher than with single-stage expansion.

One of the advantages of the process described above over the known processes resides in the low energy requirement per unit quantity of liquid produced and the simultaneous simple and reliable operation.

We claim:

1. A process for the partial liquefaction of gas mixtures by means of pressure and intense cooling, with concentration of the less readily-boiling components of said mixtures, and in which the work-performing expansion of compressed gases is utilized to generate cold, comprising the steps of compressing a gas mixture to a rela- Patented June 17, 1958 -tively low pressure of a few atmospheres, cooling the compressed mixture in a first, reversible heat-exchange zone, re-heating a minor part of the cooled, compressed mixture in heat-exchange with said mixture to approximately-the temperature of the latter, compressing said minor part to high pressures of approximately 200 at- -mospheres, cooling the highly compressed gas mixture,

expanding the resulting cooled high pressure gas mixture in a work-performing manner to approximately liquefaction pressures, partially liquefying said minor partbycooling the same in heat-exchange with the remainder of the cold, compressed gas mixture, in a second heat-exchange zone, and by throttling, expanding said remainder in a work-performing manner after said second heat-exchange zone, combining the resulting expanded gases with the non-liquefied portion of the said minor part, and leading the resulting c0ld,-expanded mixture through said first reversible heat-exchange zone to provide -a source of cold for the latter.

2. A process-according to" claim 1, comprising the further step of cooling thehighly compressed gas mixture by means of a separate source of cold before expanding the said gas mixture in a work-performing charge in-said one period -a cold, expanded gas mixture,

acting as a source of cold, two coils, one within each of said regenerators, adapted to heat a minor part of the compressed gas mixture led through'said coils in countercurrent heat-exchange -with said mixture, a liquefier adapted partially to liquefy the re-heated minor part by respective cooling in heat-exchange with the cold remainder, of said compressed gas mixture, throttling, expansion means adapted to expand said remainder leaving said liquefier, a separator adapted to divide the partially liquefied minor part into a liquefied, a non-liquefied portion and conduit means adapted to combine the expanded gases leaving said expansionmeans and said non-liquefied portion andqto lead the resulting expanded mixture alternately through each of said regenerators to act as a source of coldfor the incoming gas mixture to be treated, a second compressor for compressing the reheated minor part of said gas mixture to high pressures of approximately 200 atmospheres, a cooler associated with the high-pressure compressor for cooling the gases leaving the latter and a second expansion means for allowingthe highly compressed gas mixture leaving said second compressor to expand in a work-performing maner before beingled into the liquefier.

4. Apparatus according. to claim 3, further comprising a heat-exchanger connected between said second compressor and said second expansion means and adapted to cool the highly compressed gas mixture leaving said second compressor by means of a source of separate sources of cold. 

